OSU wide receiver Justin Blackmon and quarterback Brandon Weeden also memorialized Box via Twitter.
“Sad to hear the news about Austin Box,” Weeden tweeted. “Great guy & will be missed. My thoughts and prayers are with his family as well as his teammates.”
Sooner administrators, including President David Boren, released statements later in the day.
“The university family is deeply saddened by the tragic death of student-athlete Austin Box. Our hearts go out to his family and friends,” Boren said.
OU athletics director Joe Castiglione said grief counselors have been made available to members of the team and Box's close friends.
Chana'e Jones, a senior outfielder on the Sooner softball team, was one of Box's many friends on campus.
Together, they received their college degrees over the weekend.
“He got his degree, I got my degree,” Jones said. “It's sad to see something like this. It really opened my eyes a lot. He never gets to play football again. I get the opportunity to play softball this weekend. It puts things into perspective.”
Staff Writers Bob Przybylo and Mike Baldwin contributed to this report